Vehicles such as heavy vehicles comprising trucks having a multi cylinder internal combustion engine comprises a fuel injection system in which a pump unit provides pressurized fuel to a fuel accumulator tank based on a fuel demand. Pressurized fuel is distributed by means of fuel injectors from said accumulator tank to the cylinders for combustion. A problem that may occur is that one or more fuel injectors injects fuel unintentionally, so called unintended fuelling. Such unintended fuelling may cause serious engine damage and also after treatment damage.
A known way of diagnosing unintended fuelling is to detect pressure and possible pressure decrease in the fuel accumulator tank and determining whether the actual amount of fuel provided by the pump unit exceeds the demanded amount of fuel. If it is determined that the pressure in the accumulator tank is decreasing and/or the actual amount of fuel provided by the pump unit exceeds the demanded amount of fuel this may be caused by unintended fuelling. However, it may also be due to fuel leakage resulting in fuel not reaching the cylinders which in turn results in the pump unit providing a higher amount of fuel than the demanded amount of fuel.
US2013013175 and EP2246550 discloses detection of fuel leakage in a fuel injection system by using low pressure in the fuel accumulator tank as indicator.
There is however a need for improving accuracy in diagnosing of fuel so as to more accurately be able to diagnose unintended fuelling.